What fails, and why
On the 2008 to 2012 Escape and the cars that share its column, the worn part sits behind the lock cylinder, out of sight. A shaft inside the ignition lock housing wears until turning the key no longer carries it through to Start, which is why the cylinder and key can go back in after the repair.
Ford has written this up for its technicians. Technical service bulletin 09-19-15 covers 2008 to 2010 Focus, Escape and Mariner built on or before August 3, 2009, where the key binds at Start because the steering column lock module is damaged. A bulletin is a repair instruction, not a recall, so it does not make the repair free on a car this age.
The 2000 to 2007 Focus fails in a different place. The tumblers inside its lock cylinder wear until they stop lining up with the key, and then the key will not turn at all. Ford covered it in bulletin 05-21-17. Owners of these cars have filed 1,899 NHTSA complaints about a sticking key, a key that refuses to turn or the ignition lock itself, 837 of them for the 2000 model year.